Compositions and methods for treating precocious puberty

ABSTRACT

The present invention is directed to the controlled delivery of gonadotropin-releasing hormone (GnRH) agonists, preferably from a polymeric material that is implanted in the body. More specifically, the present invention relates to compositions comprised of a GnRH agonist, preferably histrelin, in a polymeric material that results in a desired and controlled delivery of a therapeutically effective amount of GnRH agonist over an extended period of time in order to treat central precocious puberty (CPP).

REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/155,822, filed Jun. 17, 2005, which claims priority from U.S.Provisional Application Ser. No. 60/580,520 filed Jun. 17, 2004, thecontents of which are incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention is directed to the controlled delivery ofgonadotropin-releasing hormone (GnRH) agonists, preferably from apolymeric material that is implanted in the body. More specifically, thepresent invention relates to compositions comprised of a GnRH agonist,preferably histrelin, in a polymeric material that results in a desiredand controlled delivery of a therapeutically effective amount of GnRHagonist in order to treat central precocious puberty (CPP).

There is a wide range of ages at which individuals normally startpuberty. Girls usually develop breasts and then pubic hair between theages of 8 and 13 years. Menstrual periods typically start at 12 to 13years of age. Girls will often experience moodiness and become moreirritable during puberty. Boys normally develop testicular enlargementand then pubic hair between the ages of 9 and 14 years. Underarm andfacial hair, as well as deepening of the voice, typically occur betweenthe ages of 13 and 16 years.

In the United States, an estimated one out of every 10,000 childrensuffers from central precocious puberty or premature puberty. Thiscondition is evident when girls under the age of eight years and boysunder the age of nine years develop signs of sexual maturity, such asthe early onset of secondary sexual characteristics, increase in growthrate, advancement of skeletal age beyond chronological age. Signs orsymptoms of CPP include, but are not limited to, the development ofsecondary sex characteristics such as breasts, testicle growth, or pubichair.

True precocious puberty is the result of premature initiation of thefunction of the hypothalamic-pituitary axis. Premature release of theluteinizing hormone releasing hormone (LHRH) by the hypothalamustriggers secretion of the pituitary gonadotropin hormones. As aconsequence, the gonads function at an inappropriately early age.Precocious puberty per se has many subdivisions: isosexual,heterosexual, gonadotropin-dependent (true precocious puberty),gonadotropin-independent, male-limited (familial testotoxicosis),cerebral, central, and idiopathic (unknown) precocious puberty.Precocious puberty is also known as familial testotoxicosis,gonadotropin-independent familial sexual precocity, and pubertaspraecox.

In the majority of cases of precocious puberty, the cause is unknown. Insome instances, the pituitary signals the ovaries and testicles to makefemale and male hormones at an earlier than usual time. In other cases,signs of puberty occur prematurely because of abnormalities in theovaries, testicles, or adrenal glands. Tests are usually necessary todetermine whether the cause of precocious puberty is in the brain or inanother area of the body. Usually precocious puberty is idiopathic(unknown cause). In some instances, it is due to an endocrine disorder.Cerebral precocious puberty is associated with a brain abnormality, forexample a tumor of the central nervous system, including hypothalamichamartomas, infections, head trauma, hydrocephalus, or hypothyroidism.Precocious puberty may also be a feature of McCune-Albright syndrome,neurofibromatosis, Russell-Silver syndrome and disorders of the adrenalglands. Affected individuals may encounter psychological problems due totheir accelerated growth and may feel alienated from their peers. Theymay exhibit increased aggressiveness and hyperactivity. Male-limitedprecocious puberty (familial testotoxicosis) is considered hereditary.

In females, the breasts start to develop before age 8, or menstruationoccurs before age 10, and growth is rapid. In males, onset is before age10; boys grow facial, underarm, and pubic hair; growth, including thatof the penis, accelerates; the voice deepens; and behavior becomes moreaggressive. Puberty may take place before age 3 in some children.Children with precocious puberty are taller than their peers. Since bonematurity is usually hastened in precocious puberty, closure of growthoccurs prematurely, and patients are short in stature in adulthood. Inisosexual precocious puberty, feminizing signs appear in girls,masculinization in boys. Heterosexual precocious puberty causes signs ofmasculine characteristics in girls and feminization in boys. Cerebralprecocious puberty differs in cause but mimics true precocious puberty.Central precocious puberty is attended by changes that concern thecentral nervous system. Gonadotropin-dependent precocious puberty ismarked by high gonadotropin levels in girls. Gonadotropin-independentprecocious puberty usually affects boys, who have low levels ofgonadotropin. Idiopathic precocious puberty is associated with EEG(Electroencephalogram) irregularities in girls. The cause of the unusualbrain waves is unclear.

Treatments that affect the hypothalamic-pituitary-gonadal axis caneffectively reduce hormones to pre-pubertal levels. This may arrest andprevent further development of secondary sex characteristics. Reductionof gonadotropins will allow for normal physical and psychological growthand development. Natural maturation occurs when gonadotropins return topubertal levels following discontinuation of treatment.

GnRH (also referred to as luteinizing hormone-releasing hormone (LH-RH))acts on the anterior pituitary gland to effect release of hormones thataffect activity of the reproductive organs. GnRH is produced by thehypothalamic region of the brain and controls the reproductive cycle byacting on the anterior pituitary gland to affect release of luteinizinghormone (LH) and follicular stimulating hormone (FSH), which in turn acton the gonads to stimulate the synthesis of steroid hormones and tostimulate gamete maturation. The natural GnRH peptide is a hydrophilicdecapeptide. Agonist analogs of GnRH may be used to control fertility,for example, low doses of GnRH agonists may stimulate ovulation andlarger doses may block ovulation in females and suppress spermatogenesisin males through classic negative feedback principles.

Conventional treatment of CPP includes administration of GnRH agonists.Synthetic analogues of GnRH agonists are considered to be more effectivethan the natural agonists. Examples of GnRH agonists include, but notlimited to, leuprolide (Lupron Depot®), goserelin (Zoladex®) andhistrelin (Supprelin®), buserelin (Suprefact®), nafarelin (Synarel®) andtriptorelin (De-capeptyl®, Trelstar Depot®). Many of these formulationsinvolve monthly intramuscular injections of the drug. While usuallyeffective in suppressing gonadotropin secretion, the monthly injectionsare painful, expensive, and inconvenient (monthly visits to the clinicnurse or physician). In some patients, gonadotropin suppression is notsustained by a monthly schedule of injections and the GnRH analog needsto be administered at 3-week or even 2-week intervals (1-3). Forchildren, the daily dose of histrelin for treatment of CPP is typicallyabout 10 μg/kg/day, which is equivalent to about 300 to about 600 μghistrelin per day.

Histrelin is a synthetic nonapeptide agonist of the naturally occurringGnRH. Initially the drug stimulates release of GnRH; however, chronicuse desensitizes responsiveness of the pituitary gonadotropin, causing areduction in ovarian and testicular steroidogenesis.

In view of the foregoing, a method for treating central precociouspuberty and therapeutic compositions of GnRH agonists are provided.

SUMMARY OF THE INVENTION

The subject of the present invention is a drug delivery device useful ina method for controlled delivery of GnRH agonists, preferably histrelin,to a patient over an extended period of time. This device is useful inthe treatment of CPP.

Thus, in one embodiment, the present invention provides an implantabledrug delivery device containing histrelin. In one particular embodiment,the device is a hydrogel polymer material.

In a further embodiment, the present invention provides a method ofdelivery of a therapeutically effective amount of GnRH agonists to apatient. This method involves implanting the patient with a drugdelivery device as described herein.

In another embodiment, the present invention provides for a method ofobtaining immediate release of GnRH agonist upon implantation in apatient. Desirably, the GnRH agonist, such as histrelin, is releasedfollowing implantation to achieve therapeutically effective amounts ofhistrelin in vivo to treat CPP.

In a further embodiment, the present invention provides for a method ofpreventing loss of GnRH agonist from an implant during storage.

Other aspects and advantages of the invention will be readily apparentform the detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of the presentinvention, reference should be had to the following detailed descriptiontaken in connection with the accompanying drawings.

FIG. 1 is a graph showing the linear relationship between theequilibrium water content vs. the weight percent content ofhydroxypropyl methacrylate (HPMA) units in crosslinked HEMA/HPMApolymers at their maximum state of hydration.

FIG. 2 is a graph of the release profiles of various histrelin implantsof the present invention.

FIG. 3A is a graph of the serum histrelin concentrations for eachpatient with 1 implant (track 1) at all evaluation times and FIG. 3B isa graph of the serum histrelin concentrations for each patient with 2implants (track 2) at all evaluation times.

FIG. 4 is a graph of the Breast Tanner Scale at pretreatment and 9months following insertion of an histrelin implant of the presentinvention.

FIG. 5 is a graph of Height Velocity at pretreatment and 9 monthsfollowing insertion of an histrelin implant of the present invention.

FIG. 6 is a graph of the ratio of bone age:chronologic age atpretreatment and 9 months following insertion of an histrelin implant ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

Before the present compositions and methods are described, it is to beunderstood that this invention is not limited to the particularmolecules, compositions, methodologies or protocols described, as thesemay vary. It is also to be understood that the terminology used in thedescription is for the purpose of describing the particular versions orembodiments only, and is not intended to limit the scope of the presentinvention which will be limited only by the appended claims.

It must also be noted that as used herein and in the appended claims,the singular forms “a”, “an”, and “the” include plural reference unlessthe context clearly dictates otherwise. Thus, for example, reference toa “cell” is a reference to one or more cells and equivalents thereofknown to those skilled in the art, and so forth. Unless definedotherwise, all technical and scientific terms used herein have the samemeanings as commonly understood by one of ordinary skill in the art.Although any methods and materials similar or equivalent to thosedescribed herein can be used in the practice or testing of embodimentsof the present invention, the preferred methods, devices, and materialsare now described. All publications mentioned herein are incorporated byreference. Nothing herein is to be construed as an admission that theinvention is not entitled to antedate such disclosure by virtue of priorinvention.

As used herein, the term “about” means plus or minus 10% of thenumerical value of the number with which it is being used. For exampleabout 50% means in the range of 45%-55%.

“Controlled release” or “controlled release formulation” refers to aformulation designed to consistently release a predetermined,therapeutically effective amount of drug or other active agent such as apolypeptide or a synthetic compound below toxic levels over an extendedperiod of time, with the result being a reduction in the number oftreatments necessary to achieve the desired therapeutic effect.Preferably the amount of the drug or active agent in the implantableformulations according to embodiments of the present invention establisha therapeutically effective plasma concentration of the drug over aperiod of 1 month or longer. In the matter of the present invention, acontrolled formulation would decrease the number of treatments necessaryto achieve the desired effect in terms of decreased estradiol levels ortestosterone levels, or an improvement in symptoms associated withcentral precocious puberty. The controlled release formulations of thepresent invention achieve a desired pharmacokinetic profile in asubject, preferably commencement of the release of the active agentsubstantially immediately after placement in a delivery environment,followed by consistent, sustained, preferably zero-order or nearzero-order release of the active agent.

The terms “patient” and “subject” mean all animals including humans.Examples of patients or subjects include humans, cows, dogs, cats,goats, sheep, and pigs.

The term “pharmaceutically acceptable salts, esters, amides, andprodrugs” as used herein refers to those carboxylate salts, amino acidaddition salts, esters, amides, and prodrugs of the compounds of thepresent invention which are, within the scope of sound medical judgment,suitable for use in contact with the tissues of patients without unduetoxicity, irritation, allergic response, and the like, commensurate witha reasonable benefit/risk ratio, and effective for their intended use,as well as the zwitterionic forms, where possible, of the compounds ofthe invention.

“The term “prodrug” refers to compounds that are rapidly transformed invivo to yield the parent compounds of the above formula, for example, byhydrolysis in blood. A thorough discussion is provided in T. Higuchi andV. Stella, “Pro-drugs as Novel Delivery Systems,” Vol. 14 of the A.C.S.Symposium Series, and in Bioreversible Carriers in Drug Design, ed.Edward B. Roche, American Pharmaceutical Association and Pergamon Press,1987, both of which are incorporated herein by reference.

In addition, the compounds of the present invention can exist inunsolvated as well as solvated forms with pharmaceutically acceptablesolvents such as water, ethanol, and the like. In general, the solvatedforms are considered equivalent to the unsolvated forms for the purposesof the present invention.

The term “salts” refers to the relatively non-toxic, inorganic andorganic acid addition salts of compounds of the present invention. Thesesalts can be prepared in situ during the final isolation andpurification of the compounds or by separately reacting the purifiedcompound in its free base form with a suitable organic or inorganic acidand isolating the salt thus formed. Representative salts include theacetate, hydrobromide, hydrochloride, sulfate, bisulfate, nitrate,acetate, oxalate, valerate, oleate, palmitate, stearate, laurate,borate, benzoate, lactate, phosphate, tosylate, citrate, maleate,fumarate, succinate, tartrate, naphthylate mesylate, glucoheptonate,lactobionate and laurylsulphonate salts, and the like. These may includecations based on the alkali and alkaline earth metals, such as sodium,lithium, potassium, calcium, magnesium, and the like, as well asnon-toxic ammonium, tetramethylammonium, tetraethylammonium,methylamine, dimethylamine, trimethylamine, triethylamine, ethylamine,and the like. (See, for example, S. M. Barge et al., “PharmaceuticalSalts,” J. Pharm. Sci., 1977, 66:1-19 which is incorporated herein byreference.).

“Treatment” refers to the administration of medicine or the performanceof medical procedures with respect to a patient, for either prophylaxis(prevention) or to cure the infirmity or malady in the instance wherethe patient is afflicted.

A “therapeutically effective amount” is an amount sufficient todecrease, prevent, or ameliorate the symptoms associated with a medicalcondition. In the context of hormonal therapy it can also mean tonormalize body functions or hormone levels in disease or disorders. Forexample, a therapeutically effective amount of a controlled releaseformulation of histrelin is a predetermined amount calculated to achievethe desired effect, e.g., to effectively decrease estradiol levels ortestosterone levels in a patient or decrease the symptoms of centralprecocious puberty.

In various embodiments, the novel drug delivery device of the inventionis designed for implantation into the body of the animal to which thehistrelin formulation is to be delivered. The drug delivery devices ofthe invention are desirably implants containing histrelin in areservoir, optionally together with another active agent and/or apharmaceutically acceptable carrier. Such reservoir devices may becomposed of hydrophobic or hydrophilic polymers, co-monomers, metals, orother suitable materials. Alternatively, the drug delivery devices maybe hydrogels, or other polymeric or co-monomer materials, made up of amatrix having histrelin and any other optional active agents or carriersinterspersed throughout. Preferably, the histrelin is dispersedhomogeneously throughout the matrix. Yet other suitable implants areknown to those of skill in the art and may be readily selected.

The novel implant drug delivery devices of the invention, in a preferredaspect, are highly useful in the controlled, sustained release ofhistrelin to animals, e.g., humans, sheep, dogs, cats, turkeys, cattle,etc.

The amount of histrelin and any other agents employed in the drugdelivery devices of the invention will depend not only on the desireddaily dose but also on the number of days that dose level is to bemaintained. While this amount can be calculated empirically, the actualdose delivered is also a function of any interaction with materials andthe carrier, if employed in the device.

Thus, the drug delivery device may contain a pharmaceutically acceptablecarrier which may be in the form of suspending media, solvents, aqueoussystems, and solid substrates or matrices. These carriers are known tothose of skill in the art and are not intended to be a limitation on thepresent invention.

One aspect of the invention is a controlled release pharmaceuticalcomposition comprising histrelin acetate in a controlled releasehydrogel device. The composition of the present invention is capable ofproviding, upon administration to a patient, a release profile ofhistrelin extending over at least 2 months, preferably at least about 6months or more. In some embodiments, the histrelin may be released overa period of about 18 months to about 2 years. Preferably histrelin iscontained within the hydrogel and the formulation releases atherapeutically effective amount of histrelin over an extended period oftime. A therapeutically effective amount is an amount of histrelin,preferably histrelin acetate, that when administered to a patient orsubject, ameliorates a symptom of central precocious puberty. In apreferred embodiment, the formulation may further includepharmaceutically acceptable excipients.

When the compositions of the present invention are administered to apatient, the concentration of histrelin in the patient's plasma overtime (release profile) may extend over a period of at least 2 months,preferably about 6 months or more. In a further embodiment, thehistrelin may be released over a period of about 18 months to about 2years. The compositions may provide a mean plasma concentration ofhistrelin of about 0.2 ng/ml to about 2 ng/ml. The compositions mayprovide a mean plasma concentration at steady state of histrelin in ahuman patient of from about 0.4 ng/ml to about 0.6 ng/ml. Steady stateis the point at which the amount of drug administered over a dosinginterval equals the amount of drug being eliminated over that sameperiod.

The hydrogel is a homogeneous homopolymer or copolymer having apredetermined equilibrium water content (EWC) value formed by thepolymerization of a mixture of ethylenically unsaturated monomer A andethylenically unsaturated monomer B, for example, 2-hydroxyethylmethacrylate (HEMA) and hydroxypropyl methacrylate (HPMA). Thepredetermined EWC may be calculated by determining the EWC values of thehydrogel homopolymer of hydrophilic monomer A (homopolymer A) and thehydrogel homopolymer of hydrophilic monomer B (homopolymer B);determining the relationship of the EWC values of the homogeneouscopolymers AB versus the chemical composition of said copolymers AB;selecting the targeted EWC value and determining the chemicalcomposition of copolymer AB having the targeted EWC value; forming apolymerizable mixture of monomer A and monomer B in amounts sufficientto yield copolymer AB having the targeted EWC value; and effect thepolymerization reaction to yield copolymer AB characterized by thetargeted EWC value.

Liquid polymerizable material useful in the hydrophilic products includea wide variety of polymerizable hydrophilic, ethylenically unsaturatedcompounds, in particular, hydrophilic monomers such as the monoester ofan acrylic acid or methacrylic acid with a polyhydroxy compound havingan esterifiable hydroxyl group and at least one additional hydroxylgroup such as the monoalkylene and polyalkylene polyols of methacrylicacid and acrylic acid, e.g., 2-hydroxyethyl methacrylate and acrylate,diethylene glycol methacrylate and acrylate, propylene glycolmethacrylate and acrylate, dipropylene glycol methacrylate and acrylate,glycidyl methacrylate and acrylate, glyceryl methacrylate and acrylate,and the like; the 2-alkenamides, e.g., acrylamide, methacrylamide, andthe like; the N-alkyl and N,N-dialkyl substituted acrylamides andmethacrylamides such as N-methylmethacrylamide,N,N-dimethylmethacrylamide, and the like; N-vinylpyrrolidone; thealkyl-substituted N-vinylpyrrolidones, e.g., methyl substitutedN-vinylpyrrolidone; N-vinylcaprolactam; the alkyl-substitutedN-vinylcaprolactam, e.g., N-vinyl-2-methylcaprolactam,N-vinyl-3,5-dimethylcaprolactam, and the like. Acrylic and methacrylicacid can also be useful in these formulations.

Mixtures of hydrophilic monomers are employed in the polymerizationreaction. The type and proportion of monomers are selected to yield ahomogeneous polymer, preferably a crosslinked homogeneous polymer, whichon hydration possesses the desired EWC value for the contemplatedapplication or use. As shown in FIG. 1, this value can be predeterminedby preparing a series of copolymers using different monomer ratios,e.g., mixtures of HEMA and HPMA of varying ratios, ascertaining the EWCvalues of the copolymers, and plotting the relationship of % HPMA (or %HEMA) units in the HPMA/HEMA copolymers vs. weight percent EWC of thecopolymers.

In some instances the polymerization of certain hydrophilic monomericmixtures may result in homogeneous hydrophilic copolymers whichdissolve, to a varying extent, in an aqueous medium. In such cases, asmall amount, e.g., up to 3 percent, of a copolymerizablepolyethylenically unsaturated crosslinking agent can be included in themonomeric mixture to obtain homogeneous crosslinked copolymers which arewater-insoluble as well as water-swellable. Slightly crosslinkedhomopolymer of HEMA has a EWC value of about 38%. Crosslinked copolymersof HEMA and HPMA have EWC values below 38%. On the other hand,crosslinked copolymers of HEMA and acrylamide exhibit EWC values above38 w/v %, e.g., upwards to approximately 75 weight %, and higher.Therefore, depending on the useful or effective elution rate of theactive compound, e.g., drug, that is required of a hydrogel deliverysystem for a particular application, one skilled in the art, byfollowing the teachings disclosed herein, can tailor-make copolymerhydrogel membranes which will elute the drug at the required rate.Preferred copolymers contain about 15 to 70 weight % of HEMA units andfrom about 85 to 30 weight % of units of a second ethylenic monomer andpossess predetermined EWC values in the range of from about 20 to about75%, preferably 25%. Highly preferred homogenous copolymers are thosemade from hydrophilic monomeric mixtures containing from about 80 weight% HPMA, and from about 20 weight % HEMA. In further embodiments, themixture may further contain a small amount of a polyethylenicallyunsaturated crosslinking agent, e.g., trimethylolpropane trimethacrylate(“TMPTMA”).

Various aspects of the invention include homogeneous hydrophiliccopolymers whose homogeneous polymer structure is formed via thepolymerization of a mixture of hydrophilic monomers describedpreviously; and the drug delivery device which utilize the homogeneouspolymer cartridges in the delivery system. The polymerization of amixture of hydrophilic monomers and hydrophobic monomers yieldsheterogeneous polymers. When hydrophobic segments are present in thepolymer, the interfacial free energy increases thus enhancing proteinadsorption and mineralization after implantation in an animal. Hydrogelsof polyHEMA were measured to have interfacial free energy close to zero.According to the interfacial free energy interpretation, hydrogels ofstrictly hydrophilic components would strongly appear to bebiocompatible with body tissue. Slightly crosslinked polyHEMA is ahomogeneous, hydrophilic “homopolymer” (disregarding the relativelysmall quantities of polymerized crosslinking agent therein) ofrelatively fixed characteristics or values. Techniques of altering the“homopolymer” polyHEMA to impart to it additional characteristics orproperties are difficult, time-consuming, and oftentimes result inerratic property behavior. On the other hand, mixtures of HEMA withvarying quantities of other polymerizable hydrophilic comonomer(s) canbe polymerized to give predictable homogeneous hydrophilic copolymershaving (predetermined) tailor-made properties.

Useful crosslinking agents which can be included in the polymerizablereaction medium include, for example, the polyethylenically unsaturatedcompounds having at least two polymerizable ethylenic sites, such as thedi-, tri- and tetra-ethylenically unsaturated compounds, in particular,the tri-unsaturated crosslinking agents with/without the di-unsaturatedcrosslinking compounds, for example, divinylbenzene, ethylene glycoldimethacrylate and diacrylate, propylene glycol dimethacrylate anddiacrylate; and the di-, tri- and tetra-acrylate or methacrylate estersof the following polyols: triethanolamine, glycerol, pentaerythritol,1,1,1-trimethylolpropane; and others.

The polymerization reaction can be carried out in bulk or with an inertsolvent. Suitable solvents include water; organic solvents such aswater-soluble lower aliphatic monohydric alcohols as well as polyhydricalcohols, e.g., glycol, glycerine, dioxane, etc.; and mixtures thereof.

Compounds useful in the catalysis of the polymerizable ethylenicallyunsaturated compounds include the free-radical compounds and/orinitiators of the type commonly used in vinyl polymerization such as theorganic peroxides, percarbonates, hydrogen peroxides, and alkali metalsulfates. Illustrative examples include cumene hydroperoxide, t-butylhydroperoxide, benzoyl peroxide,bis(4-t-butylcyclohexyl)peroxydicarbonate, hydrogen peroxide,2,4-dichlorobenzoyl peroxide, acetyl peroxide, di-n-propylperoxydicarbonate, di-t-butyl peroxide, di-sec-butyl peroxydicarbonate,ammonium sulfate, potassium sulfate, and sodium sulfate. A preferredcatalyst is one which is effective at moderately low temperature such asat about 20°-80° C., such as tert-butyl peroctoate, benzoyl peroxide,and di(secbutyl)peroxydicarbonate. A conventional redox polymerizationcatalyst can also be employed. Preferably, polymerization of theethylenic compounds can be effected using radiation, e.g., U.V., X-Ray,gamma radiation, microwave, or other well-know forms of radiation. Apreferred catalyst for U.V. cure is benzoin methyl ether. Catalystsand/or initiators and/or radiation are employed in a catalyticallyeffective amount to optimize the polymerization reaction.

In a preferred embodiment, small cylindrically shaped implantscontaining within their core histrelin, preferably histrelin acetate,and optionally, a pharmaceutically acceptable carrier. The membranethickness (between the interior and exterior surfaces) of the implant issubstantially uniform, and serves as a rate-limiting barrier for therelease of the contained agent. Such implants can be plasticized orhydrated and reshaped into other geometrically shaped articles for usein various medical applications. The hydrophilic implant as a xerogel,readily absorbs water. In a hydrated state it is referred to as ahydrogel. In either form, it is biocompatible and non-toxic to the hostand non-biodegradable. It is, of course, water-swellable andwater-insoluble. When the hydrogel attains its maximum level ofhydration, the water content of the hydrogel is referred to as“equilibrium water content”. The percent water content of the hydrogel(any state of hydration) is determined as follows:

$\frac{{{weight}\mspace{14mu} {of}\mspace{14mu} {hydrogel}} - {{weight}\mspace{14mu} {of}\mspace{14mu} {dry}\mspace{14mu} {polymer}\mspace{14mu} ({xerogel})}}{{weight}\mspace{14mu} {of}\mspace{14mu} {hydrogel}} \times 100$

In the manufacture of the implantable formulation, several factors areconsidered. The release profile (delay time, release rate, and duration)is determined; the hydrophilic polymeric material is identified; and thediffusivity of the active agent through it (as a rate-limiting membrane)is measured. The hydration profile of the rate-limiting membrane for agiven active agent may be readily determined by preparing a film of theselected polymer and subjecting it to a diffusion study, using a twocompartment vertical glass cell, as is well known in the art.

The diffusion coefficient and the water content at which diffusionbegins (i.e., below which substantially no diffusion occurs—hereinafter“% H_(d)”) are determined. A series of membranes is prepared fromvarious polymers. The membranes are then hydrated to their capacity andtheir equilibrium water contents are measured. The fully hydratedmembranes are placed in the two-compartment, vertical glass cells tomeasure and plot the diffusion of the macromolecular composition throughthe membrane materials at the various equilibrium water contents. Theequilibrium water content of the most hydrated membrane through which nodiffusion is detected (i.e., none of the active agent diffuses into thereceptor cell) is the % H_(d) for the system being tested. This can beaccomplished by plotting a curve of the permeability vs. equilibriumwater content.

The permeability results (diffusion coefficients) are obtained accordingto Fick's First Law of Diffusion, by use of the equation:

$\frac{Q}{t} = \frac{{APC}_{d}}{1}$

wherein dQ/dt is the flux through the membrane material (μg/hr); it ismeasured as the slope of the linear part of the curve of cumulativetransport versus time; wherein A is the area of the membrane (cm²);wherein P is the membrane's permeability coefficient (cm²/hr), orDK_(d), wherein D is the diffusivity of the membrane (cm²/hr), and K_(d)is the partition coefficient for the membrane/donor solution; wherein 1is the membrane thickness as measured at the end of the experiment (cm);and wherein C_(d) is the concentration of the donor solution (μg/cm³).

The release delay profile is then determined. Another series ofpolymeric membranes can be prepared, again varying the amounts ofcrosslinker and monomers. These membranes are then hydrated, but onlypartially, i.e., to a water content less than or equal to % H_(d). Thepartially hydrated membranes are placed in two-compartment verticalglass cells to measure and plot the diffusion of the active compoundthrough the membranes versus time. Buffer solutions for the donor andreceptor cells may be selected to contact the partially hydratedmembranes and further hydrate them at approximately the same rate atwhich they will hydrate in the delivery environment. The time betweencommencement of the diffusion study, i.e., addition of the active agentto the donor cell, and the detection of a pharmaceutically effectiveconcentration of the active agent in the receptor cell is the releasedelay time for that combination of polymer and initial percenthydration.

In order to determine the physical dimensions of thecylindrically-shaped device, the total amount of active agent to bedelivered must be determined. This is the product of the desired dailydosage and the duration of delivery. In preferred embodiments, theduration of delivery is at least about 2 months, more preferably about 6months or longer and the desired daily dosage is, for example, about 60μg to about 70 μg of histrelin.

The volume of the cylindrical reservoir (core) of a cylindrically-shapeddevice is equal to Πr_(i) ² h wherein r_(i) is the radius of thereservoir and h is its height. The formula for steady state release froma cylinder is:

[dQ/dt]=[2ΠhK _(d) C _(d)]/[In(r _(o) /r _(i))]

wherein r_(o) is the outside radius of the cylindrical device; andwherein C_(d) is the concentration of drug in the donor solution, i.e.,the carrier. Steady state release is obtained when C_(d) is maintainedat saturation. The thickness of the membrane needed for the desiredsustained release is, therefore, r_(o)−r_(i).

The amount of active agent employed will depend not only on the desireddaily dose but also on the number of days that dose level is to bemaintained. While this amount can be calculated empirically, the actualdose delivered is also a function of any interaction with materials andthe carrier, if employed in the device.

In various embodiments, the novel formulation of the present inventionmay contain a pharmaceutically acceptable carrier which may include, butis not limited to, suspending media, solvents, aqueous systems, andsolid substrates or matrices.

Suspending media and solvents useful as the carrier include, forexample, oils such as silicone oil (particularly medical grade), cornoil, castor oil, peanut oil and sesame oil; condensation products ofcastor oil and ethylene oxide; liquid glyceryl triesters of a lowermolecular weight fatty acid; lower alkanols; glycols; polyalkyleneglycols.

The aqueous systems include, for example, sterile water, saline,dextrose, dextrose in water or saline, and the like. The presence ofelectrolytes in the aqueous systems may tend to lower the solubility ofthe macromolecular drug in them.

The solid substrates or matrices include, for example, starch, gelatin,sugars (e.g., glucose), natural gums (e.g., acacia, sodium alginate,carboxymethyl cellulose), and the like.

The carrier may also contain adjuvants such as preserving, stabilizing,wetting and emulsifying agents, and the like.

The hydrating liquid useful in the practice of the invention istypically a liquid simulating the environment in which the activecompound will be released, e.g., body fluid, sterile water, tear fluid,physiological saline solution, phosphate buffer solution, and the like.While liquids other than water are useful as the hydrating liquid, thedegree to which a hydrophilic membrane is hydrated is referred to as its“water content”.

By the expressions “copolymer AB” or “copolymer AB consists essentiallyof monomer A units and monomer B units” is meant that the additioncopolymerization of monomer A and monomer B has been effected throughthe polymerizable ethylenic bond of the said monomers. By way ofillustration, if monomer A is 2-hydroxyethyl methacrylate and monomer Bis N-methylacrylamide, copolymer AB contains recurring monomer A unitsand recurring monomer B units.

Unless the context indicates otherwise, the term “copolymer” includespolymers made by polymerizing a mixture of at least two ethylenicallyunsaturated monomers.

By the term “HEMA unit(s)” is meant the structure

recurring in the polymer obtained by polymerizing hydrophilic materialcontaining 2-hydroxyethyl methacrylate (“HEMA”).

By the term “HPMA unit(s)” is meant the structure

obtained by polymerizing hydrophilic material containing hydroxypropylmethacrylate (“HPMA”).

In one embodiment, a pharmaceutical formulation of the present inventioncomprises a formulation of histrelin within a mixture of HEMA and HPMAcopolymer, preferably about 45% HEMA and 55% HPMA. In preferredembodiments, the pharmaceutical formulation comprises about 25 to about150 milligrams of histrelin, preferably about 35-45 milligrams ofhistrelin base. The formulation may further comprise between about 0.5%to about 20% excipients. In a preferred embodiment, the formulationfurther comprises about 2% stearic acid.

In one suitable embodiment, hydrogels are suited as implantable deliveryvehicles for use in delivery of histrelin according to the presentinvention. One hydrogel is prepared by mixing about 60 weight percent toabout 95 weight percent comonomers, at least one of which ishydrophilic, and sufficient amounts of a crosslinker and a liquiddiffusion enhancer which is miscible with the comonomers, to yield ahomogenous copolymer hydrogel having the equilibrium water content (EWC)value in the range from about 20% to about 85%. More preferably,homogenous copolymer hydrogel has a EWC value in the range from about25% to about 35%. More preferably, another hydrogel is prepared bymixing about 40 weight percent to about 95 weight percent comonomers, atleast one of which is hydrophilic, and sufficient amounts of acrosslinker and optionally a liquid diffusion enhancer which is misciblewith the comonomers, to yield a homogenous copolymer hydrogel having theequilibrium water content (EWC) value in the range from about 20% toabout 85%, more preferably from about 25% to about 35%.

The polymerizable liquid mixture may also contain about 1 weight percentto about 50 weight percent diffusion enhancer which may be readilyselected from among C1-C4 alkyl alcohol, allyl alcohol, tetrahydrofurylalcohol, cyclohexyl alcohol, diethylene glycol, polyethylene glycols,glycerol, acetone, ethylene glycol monomethyl ether, ethylene glycolmonoethyl ether, glyceryl isopropylidene ether dioxane, tetrahydrofuran;ethyl acetate; dimethyl sulfoxide; water, and mixtures thereof. Thecrosslinker and comonomers may be readily selected by one of skill inthe art. Hydrogels and methods of preparation are generally described inInternational Patent Application Number PCT/US00/01664, filed Jan. 26,2000 for “Hydrogel Compositions Useful for the Sustained Release ofMacromolecules and Methods of Making Same.” Other suitable hydrogels maybe readily selected by one of skill in the art. See, e.g., U.S. Pat.Nos. 5,266,325; 4,959,217; and 5,292,515.

Another particularly desirable hydrogel is prepared by mixing about 40weight percent to about 95 weight percent comonomers, at least one ofwhich is hydrophilic, and sufficient amounts of a crosslinker andoptionally a liquid diffusion enhancer which is miscible with thecomonomers, to yield a homogenous copolymer hydrogel having theequilibrium water content (EWC) value in the range from about 20% toabout 85%. More preferably, homogenous copolymer hydrogel has a EWCvalue in the range from about 25% to about 35%.

In one embodiment, the hydrogel comprises 2-hydroxyethyl methacrylate(HEMA) and hydroxypropyl methacrylate (HPMA). The hydrogel may alsofurther comprise a crosslinking agent, such as, for example (TMPTMA). Ina preferred embodiment, the hydrogel comprises about 45% of HEMA, about54.5% HPMA and about 0.5% TMPTMA.

In a further embodiment, a delivery device capable of providing asustained release of a therapeutically effective amount of GnRH agonistis provided. Preferably the controlled release is achieved of a periodof time of at least 6 months or more, more preferably about 1 to about 2years. In a preferred embodiment, the delivery device comprises ahydrogel, wherein the composition of the hydrogel is based upon thedesired daily dose and release profile. In a preferred embodiment, adelivery device capable of providing controlled release of about 60 μgto about 70 μg of histrelin per day is provided. In a more preferredembodiment, the delivery device provides about 65 μg of histrelin perday.

While not bound by theory, the diffusion of the drug occurs throughwater channels in the hydrogel. Controlling the water content of thehydrogel allows for manipulation of the release profile of the agentwithin the hydrogel. The release may also be manipulated by the geometryof the drug delivery device, including, for example, the area, wallthickness and diameter. Treatment of particular diseases or conditionsmay require higher or lower therapeutic levels or differing releaseprofiles, which may be achieved through the design of the drug deliverydevice of the present invention.

The hydrating liquid useful in the hydrogels used in the invention istypically a liquid simulating the environment in which the activecompound will be released, e.g., body fluid, sterile water, tear fluid,physiological saline solution, phosphate buffer solution, and the like.While liquids other than water are useful as the hydrating liquid, thedegree to which a hydrophilic membrane is hydrated is referred to as its“water content.”

In another suitable embodiment, the implant may be in the form of anosmotic pump, such as described by Alza (see, e.g., U.S. Pat. Nos.4,285,987 and 5,273,752) or Merck (see, e.g., European Patent No.314,206), among others. In another example, the implant device may becomposed of a hydrophobic membrane material, such as ethylmethacrylate(EMA) and ethylenevinylacetate (EVA). Other suitable implant deliverydevices include bioresorbable polymer systems (see, e.g., InternationalPatent Application No. WO98/44964, Bioxid and Cellomeda; U.S. Pat. Nos.5,756,127 and 5,854,382). Suitable bioresorbable implant devices havebeen described in the literature and may be composed of, for example,polyesters, polyanhydrides, or lactic acid/glycolic acid copolymers(see, e.g., U.S. Pat. No. 5,817,343 Alkermes Inc.).

Regardless of whether the delivery device is composed of a hydrogel,EVA/EMA polymer, bioresorbable material, metal or other material, thedevices useful in the invention(s) provide sustained release ofhistrelin over extended periods of time. This time period may range froma month to a year or several years, depending on the desiredadministration regimen. Preferably, histrelin will be released in dailydoses over a period of about 2 months or longer, and preferably over aperiod of about six months to one year or longer. In some embodiments,the histrelin may be released over a period of about 18 months to about2 years. It is to be understood that this time factor is a variabledepending on the rate-releasing membrane of choice, its interconnectingpore structure, the solubility of the active compound(s) in the liquidmedium, and other considerations well known to those skilled in the art.

Where the delivery device is composed of a hydrogel, it may be preparedsuch that the hydrogel forms the walls of a cavity which contain theactive agent. A predetermined amount of histrelin per se or an admixturewith an inert, non-toxic material or as a suspension in a non-toxicmaterial or as a suspension in a non-toxic medium, e.g., medical gradesilicone oil, is introduced into the cavity to partially fill the core.The void in the core is thereafter sealed to prevent leakage into or outof the vesicle. Preferably this can be accomplished by introducingsufficient polymerizable material into the void to cover the layer ofinert material or to substantially or completely fill the void andthereafter effecting a polymerization reaction to form a plug ofwater-swellable, water-insoluble polymer which seals the opening of thevesicle. The hydrophilic polymer plug, upon maximum hydration, will havean equilibrium water content value of the hydrophilic vesicle. Usingpolymerizable material comprising ethylenically unsaturated monomer(s)and desirably crosslinking agent(s), a polymer plug grafted to the innersurface of the vesicle can be obtained.

In a currently desired embodiment, hydrophilic cartridges are preparedby the rotational casting of polymerizable material in a tubular mold,as described in U.S. Pat. Nos. 5,266,325 and 5,292,515, which areincorporated herein by reference.

Briefly, the internal radius of the tube is approximately 1.2 to 1.3 mm,and may be larger. The tube is rotated about its longitudinal axis whichis maintained parallel to the ground. Rotational speeds are of the orderof 2150 rpm, though greater or lesser speeds could be used, e.g., 1000rpm or less to 3000 rpm and more. The tubes are fabricated ofpolyethylene, polypropylene, glass, or other suitable materials. Whenthe polymerizable mixture within the spinning tube stabilizes to thepredetermined shape, U.V. light at a distance of less than one foot isthen directed at the spinning tube for several minutes, e.g., about 7minutes, to polymerize the mixture to the shaped product. The shapedproduct is cured and annealed as follows: Thermal Cure: 60 minutes at65° C.; Postcure: 30 minutes at 95° C.; Annealing: 30 minutes at 115° C.with gradual cooling to about 25° C.

After shaping and polishing the closed end of the cartridge to anoval-like cylindrical profile, there is obtained smallcylindrically-shaped objects having smooth, unscored cylindricalsurfaces. The cartridge may be of any desired combination of dimensions.For example, the internal radius may be about 0.98 mm; the externalradius may be about 1.3 mm; and the length may be about 25 mm, or oflarger or smaller dimensions, as desired.

Smooth, unscored cylindrically-shaped objects of various lengths, e.g.,up to 25 cm and longer, can also be prepared in accordance with theteachings herein.

Such objects, in a hydrated state or plasticized with a non-toxic,biocompatible material, can be formed into desired shapes. A ring shape,for use as pessaries, surgical implants, etc. Yet other drug deliverydevices and implant shapes may be prepared using techniques known tothose of skill in the art or purchased from commercial sources.

In preferred embodiments, upon hydration the length of the implantabledelivery device is about 32-37 mm, the outside diameter is about 3-3.5mm, the cartridge walls are about 0.5 mm and the cavity diameter isabout 2-2.5 mm.

In a further embodiment, the invention provides for a method ofdelivering histrelin, alone or in combination with other active agents,upon implantation in a patient. The hydrogel delivery device of thepresent invention is hydrated with a hydrating liquid prior toimplantation in the patient, so as to provide release of histrelin uponimplantation.

In another embodiment, a method of inhibiting release of histrelin priorto implantation is provided. The hydrogel implant delivery device of thepresent invention is stored in a hydrating liquid prior to implantationin the patient, so as to limit release of histrelin from the implantprior to implantation. In preferred embodiments, the hydrating liquid issodium chloride solution.

The invention provides a method of delivering histrelin, alone or incombination with other active agents, to a veterinary or human patientin need thereof. Typically, such a patient has a disease or conditionsuch as central precocious puberty.

In order to treat a patient, one or more delivery devices as describedherein can be implanted subcutaneously in an animal by perforation. Suchdevices are characterized by a length of 10 to 50 mm, or less (e.g., 6to 9 mm), an external diameter of 2 to 5 mm, or less (e.g., 1.5 to 1.9mm). The dimensions of the device (e.g., a cartridge) can vary outsideof the limits stated above depending, in particular, on the medicalapplication involved. Animals such as sheep, cows, goats, cattle, andlarge animals, in general, can tolerate implantation by perforation oflarger dimensional drug delivery devices. Implantation can be effectedby other means, e.g., open surgery.

In one embodiment, the drug delivery device is a biodegradable matrix,which is bioresorbed and eliminated from the body following completionof the course of therapy, e.g., at least about 2 months, or morepreferably about 12 months or longer. Alternatively, a selected deliverydevice may be removed by surgical means.

A method of treating a disease associated with a hormonal disorder isalso provided. The method may include administering histrelin andmaintaining a plasma concentration of histrelin of about 0.2 ng/ml toabout 2 ng/ml and maintaining a plasma concentration of histrelin atsteady state between about 0.4 ng/ml and about 0.6 ng/ml over anextended period of time, preferably at least about 2 months, and morepreferably about 6 months or longer. Such hormonal disorders include CPPor the like. In one embodiment, the method may comprise administeringone or more delivery devices comprising a hydrogel of about 45% of HEMA,about 54.5% HPMA, about 0.5% TMPTMA and histrelin acetate.

One embodiment is a method of decreasing estradiol levels ortestosterone levels by administering histrelin and maintaining a steadystate plasma concentration of histrelin between about 0.4 ng/ml andabout 0.6 ng/ml, over an extended period of time, preferably at leastabout 2 months, and more preferably about 6 months or longer. Anotherembodiment is a method of decreasing symptoms of CPP by administeringhistrelin and maintaining a plasma concentration of histrelin betweenabout 0.2 ng/ml to about 2 ng/ml over an extended period of time,preferably at least about 2 months, and more preferably about 6 monthsor longer.

Another embodiment is a method of treating CPP comprising administeringat least one hydrogel implant of the present invention, or two or morehydrogel implants of the present invention. In the method, each hydrogelof the two hydrogel implants administered may contain between about 25to about 150 milligrams of histrelin acetate, preferably about 40 toabout 90 milligrams of histrelin acetate, more preferably about 50milligrams of histrelin acetate and release a therapeutically effectiveamount of histrelin over a period of at least two months, preferably sixmonths or longer.

In a further embodiment, a method of treating CPP comprisesadministering one or more implants comprising a hydrogel and histrelin.Preferably, the hydrogel implants contain about 50 milligrams ofhistrelin acetate and release from about 60 μg to about 70 μg ofhistrelin acetate substantially upon implantation for a period of atleast 2 months, more preferable for about 1 year.

Another aspect is a therapeutic composition of a hydrogel and histrelin,wherein, upon implantation, histrelin is released at a rate thatprovides and/or maintains a C_(ss) of about 0.2 ng/ml to about 2 ng/ml.A further embodiment is a therapeutic composition of a hydrogel andhistrelin, wherein, upon implantation, the histrelin is released at anaverage rate of from about 60 to about 70 μg/day, preferably an averageof about 65 μg daily over an extended period of time, preferably atleast about two months, more preferably about six months or longer.

Another embodiment is a controlled release formulation comprisinghistrelin and a hydrophilic polymer, which permits release of thehistrelin at a rate of about 60 μg to about 70 μg per day over about sixmonths or longer in vitro. In a further embodiment, the hydrophilicpolymer of the formulation permits release of histrelin at an averagerate of about 65 μg per day in vitro.

In a further embodiment, a controlled release formulation comprisinghistrelin and a hydrophilic polymer is provided that releases from about140 μg to about 40 μg per day over about six months or longer, morepreferably about 135 μg to about 60 μg per day over about six months orlonger.

The amount of a pharmaceutically acceptable histrelin, salt, solvated,or prodrug thereof included in the pharmaceutical composition of thepresent invention will vary, depending upon a variety of factors,including, for example, the specific histrelin used, the desired dosagelevel, the type and amount of hydrogel used, and the presence, types andamounts of additional materials included in the composition. The amountof histrelin, or a derivative thereof, in the formulation variesdepending on the desired dose for efficient drug delivery, the molecularweight, and the activity of the compound. The actual amount of the useddrug can depend on the patient's age, weight, sex, medical condition,disease or any other medical criteria. The actual drug amount isdetermined according to intended medical use by techniques known in theart. The pharmaceutical dosage formulated according to the invention maybe administered about once every six months as determined by theattending physician.

Typically, the histrelin is formulated in the implant or otherpharmaceutical composition in amounts of about 25 milligrams to about150 milligrams, preferably about 40 to about 90 milligrams of histrelin.Preferably, the amount of histrelin in the composition is formulated torelease from about 60 μg to about 70 μg of histrelin daily and maintaintherapeutic levels in the patient's blood at about 0.2 ng/ml to about 2ng/ml over an extended period of time.

The hydrogel device in which histrelin is contained provides acontrolled release of histrelin into the plasma of the patient.Hydrogels suitable for controlling the release rate of histrelin for usein the pharmaceutical compositions of the present invention includepolymers of hydrophilic monomers, including, but not limited to HPMA,HEMA and the like. Such hydrogels are also capable of preventingdegradation and loss of histrelin from the composition.

In one embodiment, a pharmaceutical formulation of the present inventioncomprises histrelin acetate contained within a hydrophilic copolymer of2-hydroxyethyl methacrylate and hydroxypropyl methacrylate. In apreferred embodiment, the copolymer of the pharmaceutical formulationcomprises about 45% HEMA and about 55% HPMA. In another preferredembodiment, the formulation further comprises stearic acid.

The amount of the hydrogel included in the pharmaceutical composition ofthe present invention will vary depending upon a variety of factors,including, for example, the specific matrix used, its molecular weight,its hydrophilicity, the type and amount of histrelin used, and thepresence, types and amounts of additional materials included in thecomposition.

The size, shape and surface area of the implant may also be modified toincrease or decrease the release rate of histrelin from the implant.

The formulations of the present invention exhibit a specific, desiredrelease profile which maximizes the therapeutic effect while minimizingadverse side effects. The desired release profile may be described interms of the maximum plasma concentration of the drug or active agent(C_(max)) and the plasma concentration of the drug or active agent atsteady state (C_(ss)).

Suitably, treatment of CPP or related conditions using the drug deliverydevices of the invention may be readily combined with other therapiesadministered by routes other than through the use of an implantabledevices. For example, treatment with histrelin according to theinvention may be combined with other treatments or therapies.

The following examples are provided to illustrate the invention and donot limit the scope thereof. One skilled in the art will appreciate thatalthough specific reagents and conditions are outlined in the followingexamples, modifications can be made which are meant to be encompassed bythe spirit and scope of the invention.

Example 1

Hydrogel implants were prepared in accordance with the presentinvention. In particular, about 45% HEMA, 54.5% HPMA and about 0.5%TMPTMA were admixed with 0.3% benzoinmethylether (BME) and 0.1%percadox-16 .

Example 2

Ten histrelin implants were prepared in accordance with the presentinvention. In particular, the histrelin implants comprised about 45%HEMA and about 55% HPMA. The resulting hydrogel implants exhibited anequilibrium water content (EWC) of about 29%. The implants wereprehydrated. The release rates were measured over sixty weeks. Therelease profile for the histrelin implants is provided in FIG. 2.

Example 3

This was an open-label study in which children with CPP were assigned toreceive one or two histrelin hydrogel implants, containing 50 mg ofhistrelin each, depending on their body weight and the ease of insertionof the implant, as determined on a case-by-case basis by the principalinvestigator and the surgeon performing the insertion. The histrelinimplants were supplied in about 2.0 mL of 1.8% sodium chloride solution.Following the first 9 months of the study, the children were assigned toone of two tracks. Children in the first track had their implant(s)removed, and one new implant inserted. The implant remained in place inthose in the second track. The children in both tracks continued in thestudy for an additional 9 months. In total, eleven girls ages 3 to 11years old were enrolled in this study. Ten of the 11 patients completedat least 12 months of treatment.

Study visits occurred at baseline, 4 weeks (Month 1), 3 months, and thenevery 3 months for the remainder of the study. Blood samples fordetermination of histrelin serum concentrations and determination ofhormone levels were collected at each clinic visit. GnRH challenge testswere performed with Relefact® LHRH 0.1 mg (=100 μg gonadorelin)intravenous injection before the implant insertion, at month 9, and atmonth 18 for all patients. GnRH challenge tests were also performed atevery visit after month 9 for the patients whose implant(s) remained inplace after that time. If at any visit there was incomplete hormonalsuppression or if the clinical evaluation indicated disease progression,the implant was to be removed and the child offered a new implant.

All 11 patients were being treated with the GnRH analogs when theyentered the study. The duration of treatment at study entry ranged fromless than 2 weeks to 39 months. Eight of the patients had been treatedfor 7 months or less, one for 18 months, one for 21 months, and one for39 months. The standard treatments were decapeptyl embonate (9patients), diphereline (1 patient), or both decapeptyl and diphereline(1 patient). These were administered as intramuscular depot injectionsevery 21 to 28 days. The histrelin implant was inserted anywhere from 2days to 1.5 months after the last depot injection.

Five patients were treated with two implants, and a single implant wasinserted in the remaining six patients. One of the patients with twoimplants had one removed at the time of suture removal; in analyses ofdata by number of implants, she is included in the group with oneimplant. At month 9, five patients had their implants removed and had asingle new implant inserted. The remaining six patients had theiroriginal implant(s) left in place for 18 months.

The standard GnRH treatment had suppressed estradiol levels to below 73pmol/L in 10 of the 11 patients at the time of implant insertion. Noneof these 10 patients had an estradiol level greater than 73 pmol/L atany evaluation through month 12, i.e., their values remained within theprepubertal range.

Basal luteinizing hormone (LH) and follicle stimulating hormone (FSH)levels were suppressed due to standard GnRH treatment at baseline andremained suppressed following implant insertion. Suppression of peak LHand FSH responses to GnRH testing was maintained for 9 months followingimplant insertion in all 11 girls, and for 12 months in the six girlswho had their original implants left in place and had GnRH challengetesting at 12 months.

The results of the first 12 months of the study, described below,support the safety and efficacy of the histrelin implant in patientswith CPP. This data also suggest that one implant is as effective as twoimplants in the suppression of estradiol, LH and FSH. Treatment with thehistrelin implant maintained suppression of estradiol and basal LH andFSH initiated by treatment with standard GnRH analogs.

Estradiol Levels. Table 1 displays the mean values, and mean changesfrom baseline, in estradiol levels for the ITT population during 9months of treatment. The mean values changed little over time,suggesting that the suppression achieved with standard treatment for CPPwas maintained during treatment with the histrelin implant.

TABLE 1 Mean Values and Mean Changes in Estradiol (pmol/L) Through Month9 (ITT Population) All ITT Patients (N = 11) Visit (Month) N Mean (SD)Mean Change (SD) Baseline (Visit 1/Day 1) 11 36.07 (23.462) Visit 2(Month 1) 11 35.70 (19.348) −0.37 (26.839) Visit 3 (Month 3) 11 37.64(18.424)  1.56 (12.008) Visit 4 (Month 6) 11 32.56 (22.192) −3.51(15.429) Visit 5 (Month 9) 11 26.38 (19.684) −9.69 (25.012)

Table 2 displays the estradiol results for subsets of the patientscategorized by the number of implants they received. The suppression ofestradiol levels was maintained regardless of whether the patientsreceived one or two implants. Within the group of patients who receivedone implant, the results were similar regardless of baseline weight.

TABLE 2 Mean Values and Mean Changes in Estradiol (pmol/L) Through Month9 by Number of Implants (ITT Population) N Mean (SD) Mean Change (SD) 1Implant Baseline (Visit 1/Day 1) 7 34.07 (17.68)  Visit 2 (Month 1) 736.47 (22.378)  2.40 (23.574) Visit 3 (Month 3) 7 32.39 (12.510) −1.69(11.688) Visit 4 (Month 6) 7 25.33 (11.523) −8.74 (12.420) Visit 5(Month 9) 7 22.56 (17.950) −11.51 (29.223)  2 Implants Baseline (Visit1/Day 1) 4 39.58 (34.41)  Visit 2 (Month 1) 4 34.35 (15.570) −5.23(35.216) Visit 3 (Month 3) 4 46.83 (25.329)  7.25 (11.818) Visit 4(Month 6) 4 45.23 (32.252)  5.65 (17.586) Visit 5 (Month 9) 4 33.08(23.520) −6.50 (18.867)

Table 3 summarizes the estradiol results after 9 months. Suppression ofestradiol levels appeared to be maintained in patients who received newimplants at 9 months and also in patients whose original implant(s)remained in place at 9 through 12 months.

TABLE 3 Mean Values and Mean Changes in Estradiol (pmol/L) After 9Months of Treatment by Track (ITT Population) Mean Change (SD) N Mean(SD) from Baseline First Track (New Implant) Visit 5 (Month 9) 5 31.48(23.691)  −6.68 (24.968) Visit 6 (Month 12) 4 12.70 (5.560) −12.93(10.984) Second Track (1 Implant Left in Place) Visit 5 (Month 9) 522.90 (18.530) −12.20 (30.329) Visit 6 (Month 12) 5 23.56 (16.475)−11.54 (5.038) Second Track (2 Implants Left in Place) Visit 5 (Month 9)1 18.30 −12.20 Visit 6 (Month 12) 1 25.80  −4.70

LH and FSH Levels. Basal gonadotropin levels were suppressed at baselineand remained suppressed following implant insertion. The mean valuesshowed little change during the first 9 months of the study, as shown inTable 4.

TABLE 4 Mean Values and Mean Changes in LH and FSH (mIU/mL) ThroughMonth 9 (ITT Population) All ITT Patients (N = 11) N Mean (SD) MeanChange (SD) LH (mIU/mL) Baseline (Visit 1/Day 1) 11 0.47 (0.358) Visit 2(Month 1) 11 0.26 (0.163) −0.21 (0.425) Visit 3 (Month 3) 11 0.25(0.199) −0.22 (0.444) Visit 4 (Month 6) 11 0.20 (0.144) −0.28 (0.416)Visit 5 (Month 9) 11 0.20 (0.121) −0.28 (0.409) FSH (mIU/mL) Baseline(Visit 1/Day 1) 11 1.20 (0.429) Visit 2 (Month 1) 11 1.07 (0.531) −0.13(0.445) Visit 3 (Month 3) 11 1.11 (0.602) −0.09 (0.499) Visit 4 (Month6) 11 1.08 (0.517) −0.12 (0.438) Visit 5 (Month 9) 11 1.07 (0.535) −0.13(0.427)

Table 5 shows the mean values and mean changes in LH and FSH forpatients categorized the by the number of implants. The mean changes inLH were larger for patients with two implants than for those with oneimplant. The subgroup of patients with one implant showed a meandecrease in FSH during the first month of treatment. This decrease wasmaintained through month 9. The subgroup of patients with two implantsshowed a small mean increase in FSH during the first 9 months oftreatment.

The pattern of changes in LH was similar regardless of baseline weightin the subgroup of patients with one implant. The patients whoweighed >40 kg at baseline had larger mean decreases in FSH at everyevaluation (ranging from −0.37 to −0.50 mIU/mL) than did those whoweighed ≦40 kg at baseline (ranging from −0.13 to −0.25 mIU/mL).

TABLE 5 Mean Values and Mean Changes in LH and FSH (mIU/mL) ThroughMonth 9 by Number of Implants (ITT Population) N Mean (SD) Mean Change(SD) LH (mIU/mL) 1 Implant Baseline (Visit 1/Day 1) 7 0.39 (0.107) Visit2 (Month 1) 7 0.31 (0.177) −0.07 (0.198) Visit 3 (Month 3) 7 0.31(0.227) −0.07 (0.229) Visit 4 (Month 6) 7 0.23 (0.170) −0.16 (0.199)Visit 5 (Month 9) 7 0.24 (0.127) −0.14 (0.172) 2 Implants Baseline(Visit 1/Day 1) 4 0.63 (0.597) Visit 2 (Month 1) 4 0.18 (0.096) −0.45(0.635) Visit 3 (Month 3) 4 0.14 (0.068) −0.48 (0.639) Visit 4 (Month 6)4 0.14 (0.068) −0.48 (0.639) Visit 5 (Month 9) 4 0.12 (0.057) −0.51(0.620) FSH (mIU/mL) 1 Implant Baseline (Visit 1/Day 1) 7 1.19 (0.426)Visit 2 (Month 1) 7 0.93 (0.325) −0.26 (0.346) Visit 3 (Month 3) 7 0.90(0.289) −0.29 (0.353) Visit 4 (Month 6) 7 0.87 (0.287) −0.31 (0.363)Visit 5 (Month 9) 7 0.89 (0.372) −0.30 (0.420) 2 Implants Baseline(Visit 1/Day 1) 4 1.23 (0.499) Visit 2 (Month 1) 4 1.33 (0.772)  0.10(0.560) Visit 3 (Month 3) 4 1.48 (0.873)  0.25 (0.580) Visit 4 (Month 6)4 1.45 (0.666)  0.23 (0.359) Visit 5 (Month 9) 4 1.40 (0.673)  0.18(0.250)

Table 6 summarizes the LH and FSH results after 9 months of treatment.Suppression of LH and FSH levels was maintained in patients who receivednew implants at 9 months and also in patients whose original implant(s)remained in place at 9 and 12 months.

TABLE 6 Mean Values and Mean Changes in LH and FSH (mIU/mL) After 9Months of Treatment by Track (ITT Population) Mean Change (SD) from NMean (SD) Baseline LH (mIU/mL) First Track (New Implant) Visit 5 (Month9) 5 0.23 (0.174) −0.39 (0.602) Visit 6 (Month 12) 4 0.28 (0.171) −0.13(0.171) Second Track (1 Implant Left in Place) Visit 5 (Month 9) 5 0.18(0.045) −0.20 (0.158) Visit 6 (Month 12) 5 0.22 (0.045) −0.16 (0.167)Second Track (2 Implants Left in Place) Visit 5 (Month 9) 1 0.10 −0.10Visit 6 (Month 12) 1 0.10 −0.10 FSH (mIU/mL) First Track (New Implant)Visit 5 (Month 9) 5 1.42 (0.502)  0.02 (0.589) Visit 6 (Month 12) 4 1.25(0.635) −0.13 (0.772) Second Track (1 Implant Left in Place) Visit 5(Month 9) 5 0.86 (0.378) −0.28 (0.228) Visit 6 (Month 12) 5 1.04 (0.483)−0.10 (0.447) Second Track (2 Implants Left in Place) Visit 5 (Month 9)1 0.40 −0.10 Visit 6 (Month 12) 1 0.40 −0.10

Results of GnRH Challenge Test. The results of the GnRH challenge testsare summarized in Table 7 for the ITT population. At baseline, therewere mean increases in LH and FSH 20 minutes after administration ofLHRH. The mean value for LH decreased at 40 and 60 minutes, whereas thevalue for FSH remained elevated. During treatment with the histrelinimplant, there was no mean increase in LH or FSH in response toadministration of LHRH.

TABLE 7 Summary of GnRH Challenge Test Results (ITT Population) Mean N 0Min 20 Min 40 Min 60 Min LH (mIU/mL) Baseline (Visit 1/Day 1) 11 0.471.30 1.15 0.91 Visit 3 (Month 3) 5 0.22 0.22 0.28 0.22 Visit 4 (Month 6)10 0.16 0.18 0.19 0.15 Visit 5 (Month 9) 11 0.20 0.24 0.22 0.22 FSH(mIU/mL) Baseline (Visit 1/Day 1) 11 1.20 1.66 1.62 1.63 Visit 3 (Month3) 5 0.92 0.94 0.96 0.92 Visit 4 (Month 6) 10 1.11 1.10 1.09 1.11 Visit5 (Month 9) 11 1.07 1.11 1.11 1.09

The results were similar for the subsets of patients who had one or twoimplants and for the patients with one implant categorized by baselineweight.

GnRH challenge tests were done at month 12 only for patients whoseimplants were left in place at month 9 (second track). At month 12,these patients continued to show no mean increase in LH and FSH levelsin response to administration of LHRH.

These results suggest that standard GnRH analog treatment had resultedin markedly suppressed gonadotropin response to GnRH stimulation beforethe patients received the histrelin implants. Complete suppression ofpeak LH and FSH to GnRH testing was maintained for 9 months followingimplant insertion in all 11 girls and for 12 months in those whoseimplants were left in place.

IGF Levels. The mean value for IGF-1 was 350.18 ng/mL at baseline and311.82 ng/mL at month 9, yielding a mean change of −38.36 ng/mL. Themean value for IGF-BP3 was 5.47 mg/L at baseline and 6.51 mg/L at Month9, yielding a mean change of 1.04 mg/L.

No patient showed a shift from baseline to Month 9 in IGF-1 levels. Ten(91%) of the patients had values within the normal range at bothevaluations, and the remaining one (9%) patient had values above thenormal range at both evaluations.

Seven (64%) patients had IGF-BP3 values at baseline that were above thenormal range for their age and sex. One of these patients had a valuewithin the normal range at Month 9, whereas the remaining six patientshad values that remained above normal. Four (36%) patients had normalIGF-BP3 values at baseline. One of these patients had a value within thenormal range at Month 9. The remaining three patients, identified below,had shifts from within the normal range at baseline to above the normalrange at month 9.

-   -   Patient 104 (3 years old), whose value increased from 2.7 mg/L        at baseline to 5.3 mg/L at month 9 (normal range, 0.8 to 3.8        mg/L)    -   Patient 107 (8 years old), whose values increased from 4.7 mg/L        at baseline to 5.9 mg/L at month 9 (normal range, 1.2 to 4.7        mg/L)    -   Patient 110 (8 years old), whose value increased from 4.2 mg/L        at baseline to 5.9 mg/L at month 9 (normal ranges, 1.2 to 4.7        mg/L at baseline and 1.6 to 4.0 mg/L at month 9)

Bone Age by X-Ray. Determination of each patient's bone age by x-ray wasperformed at screening and again at month 9. At screening, the mean boneage was 10.10 years (range, 4.5 to 12.75 years) whereas the meanchronologic age was 8.4 years (range, 3.58 to 11.00 years). Thus, boneage was advanced compared to the chronological age in all girls at thetime of implant insertion. The bone age increased by a mean of 0.35years, to 10.46 years, at month 9. The increase in chronologic age atmonth 9 was 0.96 years. Therefore, there was no advancement in bone ageduring treatment with the histrelin implant and, in fact, the bone ageadvancement regressed during treatment.

Histrelin levels. FIG. 3A displays the serum histrelin concentrationsfor each patient with 1 implant (track 1) at all evaluation times andFIG. 3B displays the serum histrelin concentrations for each patientwith 2 implants (track 2) at all evaluation times. Histrelin levelsremained fairly constant over time for most patients.

Physical Findings. Temperature, blood pressure, heart rate, weight, andheight were measured at every evaluation. The mean changes that occurredin temperature, blood pressure, and heart rate were small, showed notime-related trends, and were not clinically meaningful.

It is difficult to interpret the mean values for height and weight forthe patients in this population whose age range (3 to 11 years) coverstimes of different rates of growth in children. Therefore, height,weight, and BMI data for each patient at baseline and month 12 weretransformed to Z-scores based on the patients' age in months and sex(data not shown) Most of the patients had values for all Z-scores thatwere between −1.96 (5^(th) percentile) and 1.96 (95^(th) percentile).The following patients had values that were outside that range:

Height adjusted for age: Patients 105 (2.02 at baseline and 1.58 atmonth 12); Patient 107 (2.48 at baseline and 2.18 at month 12); andPatient 111 (1.98 at baseline and 2.16 at month 12).

Weight adjusted for age: Patient 103 (1.98 at baseline and 1.98 at month12); Patient 107 (2.41 at baseline and 2.45 at month 12); and Patient111 (2.10 at baseline and 2.32 at month 12).

BMI adjusted for age: Patient 102 (−2.49 at baseline to −1.25 at month12); Patient 103 (2.04 at baseline and 1.95 at month 12); and Patient107 (1.88 at baseline and 2.04 at month 12).

Thus, most of these patients had Z-scores that were either above the95^(th) percentile or below the 5^(th) percentile at both baseline andmonth 12, or had values above the 95^(th) at baseline which decreased tobelow the 95^(th) percentile by month 12. The only patient with anincrease from below the 95^(th) percentile at baseline to above the95^(th) percentile at month 12 was Patient 107, for BMI only.

The height velocity at insertion and at nine months followingimplantation were measured. FIG. 5 illustrates the decrease of heightvelocity during treatment. Similarly, the bone age to chronologic ageratio was assessed at insertion and at nine months followingimplantation, as illustrated in FIG. 6.

Tanner Stage. The Tanner Stage is a subjective evaluation of sexualmaturation. For the girls enrolled in this study, pubertal stages ofbreasts and pubic hair were rated on a scale of 1 to 5, where 5represented the most advanced level of sexual maturation.

Shift tables displaying changes in Tanner Stage from screening to eachsubsequent visit are presented in FIG. 4. At screening, two (18%)patients were rated Tanner Stage 2, five (45%) were rated Tanner Stage3, and four (36%) were rated Tanner Stage 4 for breasts. All of theStage 4 patients were rated Stage 3 at every evaluation from month 3onward. One Stage 3 patient was rated Stage 2 at every evaluation frommonth 2 onward. Four Stage 3 patients were rated Stage 3 at allevaluations from month 2 to month 9. At month 12, three of thosepatients were rated Stage 3 whereas the fourth patient (Patient 101) wasrated Stage 4. The latter patient was the only patient who had anincrease in Tanner Stage for breast at any time during the study.

At screening, two (18%) patients were rated Tanner Stage 1, five (45%)were rated Stage 2, three (27%) were rated Stage 3, and one (9%) wasrated Stage 4 for pubic hair. The only Stage 4 patient was rated Stage 3at every evaluation from month 1 onward. Of the remaining patients, fewhad increases in Tanner Stage: one from Stage 1 to 2, two from Stage 2to 3, and one from Stage 3 to 4.

Results and Conclusion. The results show that the histrelin implantmaintains suppression of gonadotropins and estradiol for at least 12months in girls with CPP. Skeletal maturation was significantly advancedat the time of implant insertion, but progressed more slowly duringtreatment.

There were no deaths or other serious adverse events during the first 12months of treatment. One patient failed to complete 12 months oftreatment because of an adverse event. Patient 103 was a 10-year-oldgirl who received two implants. She developed a local infection at theimplant site, which resolved in 10 days after treatment with oralantibiotics. At Month 9, she was assigned to the first track and had hertwo original implants removed. A new implant was inserted in the sameincision. A wound infection developed approximately 1 week after the newimplant had been inserted. This infection also resolved after treatmentwith oral antibiotics. Ten days after insertion of the new implant, itwas found to be partially extruded from the incision site and wasremoved. The patient withdrew from the study after the implant wasremoved. Seven (64%) patients experienced at least one adverse eventduring the study. The most commonly reported events were conditionsrelated to the implant site and infections. All of the events were ratedmild by the investigator.

What has been described and illustrated herein are embodiments of theinvention along with some of their variations. The terms, descriptionsand figures used herein are set forth by way of illustration only andare not meant as limitations. Those skilled in the art will recognizethat many variations are possible within the spirit and scope of theinvention, which is intended to be defined by the following claims andtheir equivalents in which all terms are meant in their broadestreasonable sense unless otherwise indicated.

1. A controlled release reservoir implant containing a formulationcomprising histrelin or its pharmaceutically acceptable salt, thereservoir implant comprising a hydrophilic copolymer obtained from acopolymerization of a mixture comprising at least two hydrophilic,ethylenically unsaturated monomers, and which implant upon implantationin a patient suffering from central precocious puberty provides anaverage in vivo release rate between 60 micrograms and 70 micrograms ofthe histrelin or its salt daily in the patient.
 2. The implant of claim1 in which the at least two monomers comprise 2-hydroxyethylmethacrylate (HEMA) and hydroxypropyl methacrylate (HPMA).
 3. Theimplant of claim 1 in which the mixture comprises about 45% of HEMA andabout 55% HPMA.
 4. The implant of claim 1 in which the mixture comprisesabout 45% of HEMA, about 54.5% HPMA and about 0.5% trimethylolpropanetrimethacrylate (TMPTMA).
 5. The implant of claim 1 which provides anaverage in vitro release rate of about 65 micrograms of the histrelin orits salt per day.
 6. The implant of claim 1 which releases histrelin orits salt at a rate to maintain a mean plasma concentration of histrelinof about 0.2 ng/ml to about 2 ng/ml over at least two months.
 7. Theimplant of claim 1 which releases histrelin or its salt at a rate tomaintain a mean plasma concentration of histrelin of about 0.4 ng/ml toabout 0.6 ng/ml over at least two months.
 8. A controlled releasereservoir implant containing a formulation comprising histrelin or itspharmaceutically acceptable salt, the reservoir implant comprising ahydrophilic copolymer obtained from a copolymerization of a mixturecomprising at least two hydrophilic, ethylenically unsaturated monomers,and which implant upon implantation in a patient suffering from centralprecocious puberty provides an average in vivo release rate between 60micrograms and 70 micrograms of the histrelin or its salt daily in thepatient to maintain a mean plasma concentration of histrelin of about0.2 ng/ml to about 2 ng/ml over at least six months.
 9. The implant ofclaim 8 in which the histrelin or its salt is released at a rate tomaintain a mean plasma concentration of histrelin of about 0.4 ng/ml toabout 0.6 ng/ml over at least six months.
 10. A controlled releasereservoir implant containing a formulation comprising 50 mg histrelinacetate, the reservoir implant comprising a hydrophilic copolymerobtained from a copolymerization of a mixture comprising about 45% HEMA,54.5% HPMA and about 0.5% TMPTMA, and which implant provides an averagein vitro release rate of about 65 micrograms of the histrelin acetatedaily.
 11. The implant of claim 10 which upon implantation in a patientsuffering from central precocious puberty releases histrelin acetatedaily in the patient at a rate to maintain a mean plasma concentrationof histrelin of about 0.2 ng/ml to about 2 ng/ml over at least sixmonths.
 12. The implant of claim 11 in which the mean plasmaconcentration of histrelin is maintained over a period of about twelvemonths.